Notes on Setting Up a New iPhone
As of iOS 11, setting up a new iPhone is easier than ever. You can take the old phone and hold it near the new one to transfer wifi config and Apple ID basics. From there, a restore from iCloud takes care of most everything.
There are some things that do not come along with iCloud restore. Here's a checklist, which are things that got me when I set up my new phone the other day:
log in to every account-based app, such as Amazon, Audible. For an app like Audible, you'll want to pre-download your favorites or whatever you are listening to now.
Transfer security token app, such as Authy. Authy the app on your new phone might not maintain it's status from a restore. You can authorize a new instance from the old phone, so make sure you do that before wiping the old one.
Re-add audiobooks. I have some audiobooks that I bought outside of Audible and iBooks, and there is not a way to load them in easily. It used to be that you could sync them from iTunes, but that has just become an awful experience, if it works at all. I use an app called MP3 Books, which lets you load books over wifi from you Mac or PC. It's a little clunky: you start a file server inside the app on the phone, then connect to it from your Mac/PC as you would connect to any file server on your network. But things transfer very fast.
Load up non-iTunes movies. Suppose you have home movies or something like Star Wars Despecialized. Syncing those through iTunes is a very bad experience. You can use an app like Infuse or VLC to cross load the movies from your PC. Works very much like the books app above.
Check Find Friends and make sure the new phone is the one sharing your location with your family.
Log in to Dropbox app/Google Drive app to make sure they are connected to the iOS Files app.